Hydroxy-t-alkyl peroxyester

ABSTRACT

Hydroxy-t-akyl peroxyesters having the general structure ##STR1## where R, R 1 , R 2 , R 3  and R 4  can be alkyl moieties and having 10 hour half-life temperatures below about 75° C. (for example, 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate) are used as initiators for vinyl monomer polymerization and as catalysts for curing unsaturated polyester resins in order to improve the efficiency of the systems.

This is a divisional of co-pending application Ser. No. 496,357 filed onMay 20, 1983, now U.S. Pat. No. 4,525,308.

BACKGROUND OF THE INVENTION

This invention relates to novel hydroxy-t-alkyl peroxyesters (A) and theuse of these compositions as free-radical initiators for improved vinylmonomer polymerization processes and as curing catalysts for improvedunsaturated polyester resin curing processes.

From an economic standpoint the polymer industry wishes to increaseproduction of polymeric resins without resorting to building additionalexpensive production facilities. It is well known in the polymerizationsarts, especially in the art of polymerizing vinyl chloride, that ratesof polymerizations can be enhanced by using more active free-radicalcatalysts; thus, polymerization cycle times can be decreased andproduction capacity can be increased when this technique is employed.This phenomenon is especially useful in vinyl chloride polymerizations,since more active catalysts result in higher polymerization rateswithout simultaneously affecting polymer molecular weightcharacteristics (assuming that the temperature is not changed); hence,polymer physical properties remain unchanged. It is, also, well known inthe peroxide art that half-life characteristic (a measure of peroxideactivity) of peroxides can be changed significantly for certain classesof peroxides by employing various structural changes in the peroxide.

The hydroxy-t-alkyl peroxyesters of the present invention have beenfound to improve the efficiency of polymerization systems using lesseramounts of the initiator than were used in the prior art. The 10 hourhalf-life temperatures of compounds of the present invention aresignificantly decreased over similar prior art peroxyesters.

SUMMARY OF THE INVENTION

The present invention is directed to (A) A hydroxy-t-alkyl peroxyesterof structure (A) ##STR2## which has a 10 hour half-life temperaturebelow about 75° C., where

R₁ and R₂ are selected from an alkyl of 1 to 4 carbons,

R₃ and R₄ are selected from hydrogen or an alkyl of 1 to 4 carbons,

R₁ and R₃ can be connected together to form a lower alkyl substituted 3carbon alkylene bridge and R₃ can additionally be ##STR3## and

R is selected from ##STR4## where

R₅ is selected from hydrogen or an alkyl of 1 to 8 carbons,

R₆ is selected from an alkyl of 1 to 8 carbons,

R₇ is selected from the group consisting of an alkyl of 1 to 8 carbons,an alkenyl of 1 to 8 carbons, an aryl of 6 to 10 carbons, an alkoxy of 1to 6 carbons and an aryloxy of 6 to 10 carbons, and

R₈ and R₉ are selected from an alkyl 1 to 4 carbons;

(B) A process of polymerizing ethylenically unsaturated monomers (suchas ethylene and vinyl chloride) by using an initiating amount of thehydroxy-t-alkyl peroxyester of structure A as the initiator atappropriate temperature during the polymerization; and

(C) A process of curing unsaturated polyester resin compositions byheating such resins in the presence of a catalyzing amount of A as thecuring agents.

DETAILED DESCRIPTION OF THE INVENTION Preparations of theHydroxy-t-Alkyl Peroxyesters

The hydroxy-t-alkyl peroxyesters (A) of this invention can be preparedby reacting an appropriate acid chloride, acid bromide or acid anhydridewith a hydroxy-t-alkyl hydroperoxide in the presence of a base andoptionally in the presence of a phase transfer catalyst (PTC).Surprisingly the acylation reaction predominantly occurs at thehydroperoxy group rather than at the hydroxy group of thehydroxy-t-alkyl hydroperoxide, thus forming the inventionhydroxy-t-alkyl peroxyesters A rather than hydroperoxy-alkyl esters B.Some further reaction of A with the acylating ##STR5## agent can occurto produce small amounts of ester-t-alkyl peroxyester C. C could also beproduced to a small extent by further reaction ##STR6## of B (if itformed) with acylating agent. In general, the acid chlorides employedfor producing the hydroxy-t-alkyl peroxyesters of this invention aresterically hindered acid chlorides which readily react at thehydroperoxy group of the hydroxy-t-alkyl hydroperoxide but much lessreadily react at the hydroxy group of the hydroxy-t-alkyl hydroperoxideor at the hydroxyl group of A. Such hindered acid chlorides are derivedfrom hindered di- and tri-α-branched carboxylic acids that are listedfurther below. Less sterically hindered acid chlorides, such as thosederived from non- and mono-α-branched carboxylic acids and aromaticcarboxylic acids readily react with the hydroxy group of thehydroxy-t-alkyl peroxyester (see Example 17, infra). The inventionhydroxy-t-alkyl peroxyesters of this invention are restricted to thosederived from sterically hindered acid chlorides as defined above. Thisputs an upper 10 hour half-life temperature limit of about 75° C. on theinvention hydroxy-t-alkyl peroxyesters since one of the highertemperature invention hydroxy-t-alkyl peroxyesters,3-hydroxy-1,1-dimethylbutyl peroxy-(2-ethylhexanoate), had a 10 hourhalf-life temperature of about 66°-67° C. The non-inventionhydroxy-t-alkyl peroxyesters that are derived from less hindered acidchlorides generally would have 10 hour half-life temperatures of about90° to 100° C. (if they could be made). Hence, the inventionhydroxy-t-alkyl peroxyesters (Structure A) are much more active ininitiating polymerizations of ethylenically unsaturated monomers and incuring of unsaturated polyester resins. The preferred acid chlorides canbe prepared from the corresponding acid by reacting with acidchlorinating agents such as PCl₃, POCl₃, PCl₅, SOCl₂, phosgene (in thepresence of N,N-dimethylformamide) and benzotrichloride followed byisolation of the acid chloride product from the reaction mixture.

Carboxylic acids that are useful for producing the hydroxy-t-alkylperoxyester A of this invention include alkylarylacetic acids such as2-phenylpropionic acid 2-phenylbutyric acid, and2-methyl-2-phenylpropionic acid, alkoxypropionic acids such as2-methoxypropionic acid, aryloxypropionic acids such as2-phenoxypropionic acid, unsaturated carboxylic acids such asmethacrylic acid and 2-methyl-2-butenoic acid, α,α-dialkylacetic acidssuch as isobutyric acid, 2-ethylbutyric acid, 2-ethylhexanoic acid, and2-butyloctanoic acid and α,α,α-trialkylacetic acids (i.e., neoacids)such as pivalic acid, neohexanoic acid, neoheptanoic acid, neooctanoicacid, neononanoic acid, neodecanoic acid and neotridecanoic acid (thecompositions and structures of the latter five neoacid mixtures beingthose described in U.S. Pat. No. 3,624,123).

Hydroxy-t-alkyl hydroperoxides that are useful for producing thehydroxy-t-alkyl peroxyesters A of this invention include3-hydroxy-1,1-dimethylpropyl hydroperoxide, 3-hydroxy-1,1-dimethylbutylhydroperoxide, 1-ethyl-3-hydroxy-1-methylpentyl hydroperoxide,1,1-diethyl-3-hydroxybutyl hydroperoxide,5-hydroxy-1,3,3-trimethylcyclohexyl hydroperoxide and4-hydroxy-2,6-dimethyl-2,6-dihydroperoxyheptane. The hydroxy-t-alkylhydroperoxides can be prepared by treating the correspondinghydroxy-t-alkanols with excess hydrogen peroxide in the presence of astrong acid catalyst such as sulfuric acid, phosphoric acid, perchloricacid, the acid form of an ion exchange resin or p-toluenesulfonic acid.For instance, 1,1-dimethyl-3-hydroxybutyl hydroperoxide, also know ashexylene glycol hydroperoxide, has been prepared in this manner fromcommericially available 2-methyl-2,4-pentanediol (hexylene glycol)according to U.S. Pat. No. 3,236,872. The hydroxy-t-alkanols which areused to prepared the hydroxy-t-alkyl hydroperoxides can be prepared bymethods well known in the art. For instance, some hydroxy-t-alkanols canbe prepared by treating lactones with a Grignard agent (e.g.,methylmagnesium bromide). The hydroxy-t-alkyl hydroperoxides can also beprepared using the corresponding hydroxy-t-alkylene in place of thehydroxy-t-alkanols. Thus, treatment of a hydroxy-t-alkylene withhydrogen peroxide in the presence of a strong acid catalyst results information of the hydroxy-t-alkyl hydroperoxide.

The bases that are useful in preparing the hydroxy-t-alkyl peroxyestersA of this invention include inorganic bases such as NaOH, KOH, LiOH, Na₂CO₃ and K₂ CO₃ and organic amines such as pyridine, N,N-dimethylaniline,triethylamine, tributylamine and 1,4-diazabicyclo[2.2.2]octane. Theoptionally empolyed phase transfer catalysts include tetraalkylammoniumsalts such as tetrabutylammonium chloride, bromide and hydrogen sulfateand other reported phase transfer catalysts.

Representative of the hydroxy-t-alkyl peroxyester A of this inventionare as follows:

3-Hydroxy-1,1-dimethylbutyl peroxy-2-phenylbutyrate,

3-Hydroxy-1,1-dimethylbutyl peroxy-2-phenoxypropionate,

3-Hydroxy-1,1-dimethylbutyl peroxymethacrylate,

3-Hydroxy-1,1-dimethylbutyl peroxy-2-methylcrotonate,

3-Hydroxy-1,1-dimethylbutyl peroxyisobutyrate,

3-Hydroxy-1,1-dimethylbutyl peroxy-(2-ethylhexanoate),

3-Hydroxy-1,1-dimethylbutyl peroxy-(2-butyloctanoate),

3-Hydroxy-1,1-dimethylbutyl peroxypivalate,

3-Hydroxy-1,1-dimethylbutyl peroxyneohexanoate,

3-Hydroxy-1,1-dimethylbutyl peroxyneoheptanoate,

3-Hydroxy-1,1-dimethylbutyl peroxyneodecanoate,

3-Hydroxy-1,1-dimethylbutyl peroxyneotridecanoate,

3-Hydroxy-1,1-dimethylpropyl peroxyneohexanoate,

3-Hydroxy-1,1-dimethylpropyl peroxyneodecanoate,

3-Hydroxy-1,1-dimethylpropyl peroxypivalate,

3-Hydroxy-1,1-diethylbutyl peroxyneohexanoate,

5-Hydroxy-1,3,3-trimethylcyclohexyl peroxyneodecanoate,

4-Hydroxy-2,6-dimethyl-2,6-di(neohexanoylperoxy)heptane, and

4-Hydroxy-2,6-dimethyl-2,6-di(neodecanoylperoxy)heptane.

Vinyl Polymerizations

In the free-radical polymerizations or copolymerizations ofethylenically unsaturated monomer at suitable temperatures (andpressures) the hydroxy-t-alkyl peroxyesters A of this invention arefound to be efficient initiators (i.e., reduced initiator requirements).

Ethylenically unsaturated monomers include olefins, such as ethylene,propylene, styrene, alpha-methylstyrene, chlorostyrene, vinyltoluene,vinylbenzyl chloride, vinylpyridine and divinylbenzene; diolefins, suchas 1,3-butadiene, isoprene and chloroprene; vinyl esters, such as vinylacetate, vinyl propionate, vinyl laurate, vinyl benzoate and divinylcarbonate; unsaturated nitriles, such as acrylonitrile andmethacrylonitrile; acrylic acid, methacrylic acid and their esters andamides, such as methyl, ethyl, n-butyl and 2-ethylhexyl acrylates andmethacrylates, and acrylamide and methacrylamide; maleic anhydride;maleic and fumaric acids and their esters; vinyl halo and vinylidenehalo compounds, such as, vinyl chloride, vinyl bromide, vinyl fluoride,vinylidene chloride and vinylidene fluoride; perhalo olefins, such astetrafluoroethylene, hexafluoropropylene and chlorotrifluoroethylene;vinyl ethers, such as methyl vinyl ether, ethyl vinyl ether and n-butylvinyl ether; allyl esters, such as allyl acetate, allyl benzoate,diallyl phthalate, allyl ethyl carbonate, triallyl phosphate, diallylfumarate and diallyl carbonate; acrolein; methyl vinyl ketone; andmixtures thereof.

In this invention temperatures of 20° C. to 250° C., preferably 30° to200° C., and peroxyester levels (on a pure baise) of 0.002 to 3%,preferably 0.002 to 1% by weight based on monomer, are employed inpolymerizations or copolymerizations of ethylenically unsaturatedmonomers.

The hydroxy-t-alkyl peroxyesters A of this invention can also be used incombination with other free-radical initiators such as peroxyesterswhich include t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexanoate,t-butyl peroxyacetate, t-amyl peroxypivalate, t-butylperoxyneodecanoate, t-amyl peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate and alpha-cumyl peroxyneodecanoate; dialkylperoxydicarbonates including di- n-propyl, diisopropyl, di-(sec-butyl),dicyclohexyl, di-(4-t-butylcyclohexyl), di-(2-phenoxyethyl),di-(2-ethylhexyl) and dihexadecyl peroxydicarbonates; acyl alkylsulfonylperoxides including acetyl cyclohexylsulfonyl peroxide and acetylsec-heptylsulfonyl peroxide; diacyl peroxides including dibenzoylperoxide, didodecyl peroxide, diisobutyryl peroxide anddi-(2-methylpentanoyl)peroxide; diperoxyketals including2,2-di-(t-butylperoxy)butane; 2,2-di-(t-butylperoxy)heptane, ethyl3,3-di-(t-butylperoxy)butyrate,1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-di-(t-butylperoxy)cyclohexane and 1,1-di(t-amylperoxy)cyclohexane;monoperoxycarbonates including OO-t-butyl O-isopropylmonoperoxycarbonate and OO-t-butyl O-(2-ethylhexyl)monoperoxycarbonate;dialkyl peroxides such as 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane; andazo compounds including azobis(isobutyronitrile),2-t-butylazo-2-cyano-4-methoxy-4-methylpentane and1-t-butylazo-1-cyanocyclohexane.

CURING OF UNSATURATED POLYESTER RESINS

In the curing of unsaturated polyester resin compositions by heating atsuitable curing temperatures in the presence of free-radical curingagents, the hydroxy-t-alkyl peroxyesters A of this invention exhibitenhanced curing activity. Unsaturated polyester resins that can be curedby the peroxides of this invention usually includes an unsaturatedpolyester and one or more polymerizable monomers.

The unsaturated polyesters are, for instance, polyesters as they areobtained by esterifying at least one ethylenically unsaturated di- orpolycarboxylic acid, anhydride or acid-halide, such as maleic acid,fumaric acid, glutaconic acid, itaconic acid, mesaconic acid, citraconicacid, allylmalonic acid, allylsuccinic acid, tetrahydrophalic acid andothers with saturated or unsaturated di- or polyols, such as ethyleneglycol, diethylene glycol, triethylene glycol, 1,2- and1,3-propanediols, 1,2- 1,3- and 1,4-butanediols,2,2-dimethyl-1,3-propanediol, 2-hydroxymethyl-2-methyl-1,3-propanediol,2-buten-1,4-diol, 2-butyn-1,4-diol, 2,2,4-trimethyl-1,3-pentanediol,glycerol, pentaerythritol, mannitol and others. Mixtures of suchpolyacids and/or mixtures of such polyalcohols may also be used. Theunsaturated di- or polycarboxylic acids may be partially replaced, bysaturated polycarboxylic acids, such as adipic acid, succinic acid,sebacic acid and others and/or by aromatic polycarboxylic acids, such asphthalic acid, trimellitic acid, pyromellitic acid, isophthalic acid andterephthalic acid. The acids used may be substituted by groups such ashalogen. Examples of such suitable halogenated acids are, for instance,tetrachlorophthalic acid,5,6-dicarboxy-1,2,3,4,7,7-hexachlorobicyclo(2.2.1)-2-heptene and others.

The other component of the unsaturated polyester resin composition, thepolymerizable monomer or monomers, can be preferably ethylenicallyunsaturated monomers, such as styrene, chlorostyrene, vinyltoluene,divinylbenzene, alpha-methylstyrene, diallyl maleate, diallyl phthalate,dibutyl fumarate, acrylonitrile, triallyl phosphate, triallyl cyanurate,methyl acrylate, methyl methacrylate, n-butyl methacrylate, ethylacrylate and others, or mixtures thereof, which are copolymerizable withsaid polyesters.

A preferred resin composition contains as the polyester component theesterification product of 1,2-propylene glycol (a polyalcohol), maleicanhydride (an anhydride of an unsaturated polycarboxylic acid) andphthalic anhydride (an anhydride of an aromatic dicarboxylic acid) aswell as the monomer component, styrene.

Temperatures of about 20° C. to 200° C. and peroxide levels of about0.05% to 5% or more by weight of curable unsaturated polyester resin arenormally employed.

The unsaturated polyesters described above can be filled with variousmaterials such as sulfur, glass fibers, carbon blacks, silicas, metalsilicates, clays, metal carbonates, antioxidants, heat and lightstabilizers, sensitizers, dyes, pigments, accelerators, metal oxidessuch as zinc oxide, blowing agents, etc.

Other types of unsaturated resins can be cured using the compositions ofthis invention as curing catalysts. These resins, called unsaturatedvinyl ester resins, consist of a vinyl ester resin component and one ormore polymerizable monomer components. The vinyl ester resin componentcan be made by reacting a chloroepoxide such as epichlorohydrin withappropriate amounts of a glycol such as bisphenol A[2,2-di-(4-hydroxyphenyl)propane], in the presence of a base such assodium hydroxide, to yield a condensation product having terminal epoxygroups derived from epichlorohydrin. Subsequent reaction of thecondensation product with polymerizable unsaturated carboxylic acidssuch as acrylic acid and methacrylic acid, in the presence or absence ofacidic or basic catalysts, results in formation of a vinyl esterterminated resin component. Normally styrene is added as thepolymerizable monomer component to complete the preparation of theunsaturated vinyl ester resin.

Temperatures of about 20° C. to 200° C. and pure peroxide levels ofabout 0.05% to 5% or more by weight of curable unsaturated vinyl esterresin compositions are normally employed for curing of the unsaturatedvinyl ester resins.

The unsaturated vinyl ester resin described above can be filled with thematerials employed with the unsaturated polyester resin compositionsdescribed previously.

The hydroxy-t-alkyl peroxyesters A of this invention can also beemployed for curing of monomers such as diethylene glycol bis(allylcarbonate) (ADC) as well as other diallyl and polyallyl compounds. Inthese applications 0.1 to 10% or more of the invention peroxyesters,based on curable monomer, can be employed. Temperature profiles areusually employed in the ADC curing processes. The temperatures rangefrom about 70° C. initially to about 125° C. and the time for curing canrange up to 10 hours.

The hydroxy-t-alkyl peroxyesters A of this invention can also be used asintermediates to prepare other peroxides by reaction at the hydroxygroup.

EXAMPLES

Neohexanoyl chloride and other acid chlorides used in the preparationsof the hydroxy-t-alkyl peroxyesters of this invention, prior artperoxyesters, and other peroxyesters prepared in the examples wereprepared by procedures similar to that outlined in Example I of U.S.Pat. No. 3,624,123. 3-Hydroxy-1,1-dimethylbutyl hydroperoxide wasprepared according to the procedure outlined in Example 2 of U.S. Pat.No. 3,236,872. 7-Hydroxy-1,1,5-trimethylheptyl hydroperoxide wassimilarly prepared.

The starting material, 3-hydroxy-1,1-dimethylpropyl hydroperoxide, wasprepare using a procedure similar for preparing3-hydroxy-1,1-dimethylbutyl hydroperoxide, mentioned above; thiscompound was prepared from 3-methyl-3-buten-1-ol (0.50 mole) and 50% H₂O₂ (2.00 moles) with concentrated H₂ SO₄ (0.75 mole) as the acidcatayst. The product that was isolated was a liquid having an assay of81.2% according to hydroperoxide active oxygen content. The correctedyield was 37.9%.

EXAMPLE 1 Preparation of 3-Hydroxy-1,1-dimethylbutyl Peroxypivalate(I-1)

A jacketed reactor equipped with a mechanical stirrer, a thermometer anda dropping funnel was charged with 19.9 g (0.160 mole) of 45% KOH, 9.9 gof water, 21.5 g (0.150 mole) of 93.7% 3-hydroxy-1,1-dimethyl butylhydroperoxide (also known as 4-hydroxy-2-methyl-2-hydroperoxypentane),25 g of methylene chloride and 0.65 g (0.002 mole) of tetrabutylammoniumbromide, a phase transfer catalyst (PTC). The resulting vigorouslystirred mixture was cooled to -5° to -2° C. and to it was slowly added12.6 g (0.100 mole) of 95.4% pivaloyl chloride over a period of about 30minutes. The resulting product mixture was then stirred for 2 hours at-5° to -2° C. after which 25 g of 10% KOH and an additional 50 g ofmethylene chloride were added to the reaction mixture. The reaction masswas allowed to separate into two liquid phases at 10° C. and the lowerorganic layer was removed, dried over about 5% by weight of anhydrousMgSO₄ and after the spent desiccant was separated by filtration themethylene chloride was removed in vacuo at 0° to 10° C. Obtained was24.5 g of liquid product which had an assay of 72.3% according toperoxyester active oxygen content. The corrected yield was 81.3%. Aninfrared spectrum of the product showed a large broad OH band centeredat 3450 to 3550 cm⁻¹.

EXAMPLE 2 Preparations of Other 3-Hydroxy-1,1-dimethylbutyl Peroxyesters

The procedure utilized in Example 1 was employed for preparation ofother 3-hydroxy-1,1-dimethylbutyl peroxyesters from3-hydroxy-1,1-dimethylbutyl hydroperoxide and various carboxylic acidchlorides. The starting carboxylic acid chloride, the conditionsemployed and the yield data for these preparations are summarized inTable I. Also included in Table I are the results for Example 1. In allcases, the infrared spectrum of the product exhibited a strong and broadOH band centered at about 3400 to 3500 cm⁻¹ which showed that thedesired product was obtained.

Decomposition studies in dilute solution showed that3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate (I-3) had a 10 hourhalf-life temperature (i.e., the temperature at which half of theperoxide is decomposed in 10 hours) in trichloroethylene of 36° C. andthat 3-hydroxy-1,1-dimethylbutyl peroxy-(2-ethylhexanoate)(I-6) had a 10hour half-life temperature in benzene of about 66° to 67° C.

                                      TABLE I                                     __________________________________________________________________________    3-Hydroxy-1,1-Dimethylbutyl Peroxyesters                                      1-Hydroxy-1,1-Dimethylbutyl                                                                   Acid Chloride                                                                         Peroxidation Conditions       Infrared OH             peroxyester     Employed                                                                              Temp., °C.                                                                    Time, hrs                                                                          PTC  Assay, %                                                                           Corr. Yield,                                                                          Band,                   __________________________________________________________________________                                                          cm.sup.-1               Peroxypivalate                                                                             (I-1)                                                                            Pivaloyl                                                                              -5 to -2                                                                             2.0  TBABr*                                                                             72.3 81.3    broad, 3450-3550        Peroxyneohexanoate                                                                         (I-2)                                                                            Neohexanoyl                                                                           0 to 5 2.0  No   80.5 79.8    broad, 3450-3550        Peroxyneohexanoate                                                                         (I-2)                                                                            Neohexanoyl                                                                           0 to 5 2.0  TBABr*                                                                             77.9 90.7    broad, 3450-3550        Peroxyneodecanoate                                                                         (I-3)                                                                            Neodecanoyl                                                                           28 to 30                                                                             1.0  No   79.3 78.5    broad, 3450-3550        Peroxyneodecanoate                                                                         (I-3)                                                                            Neodecanoyl                                                                           28 to 30                                                                             1.0  TBABr*                                                                             81.8 73.8    broad, 3450-3550        Peroxyneotridecanoate                                                                      (I-4)                                                                            Neotridecanoyl                                                                        28 to 30                                                                             1.0  No   67.5 73.7    medium, 3500            Peroxyisobutyrate                                                                          (I-5)                                                                            Isobutyryl                                                                            30     1.0  No   80.2 56.6    broad, 3400-3500        Peroxy-2-ethylhexanoate                                                                    (I-6)                                                                            2-Ethylhexanoyl                                                                       10 to 15                                                                             0.5  No   85.6 84.3    sharp, 3550             Peroxy-2-phenylbutyrate                                                                    (I-7)                                                                            2-Phenylbutyryl                                                                       10 to 15                                                                             0.5  No   74.1 50.0      --                    __________________________________________________________________________     *TBABr -- Tetrabutylammonium Bromide, Phase Transfer Catalyst (PTC)      

For the sake of comparision, some of the next adjacent homologuecompounds where the atomic distance (as measured by intervening atoms)between the hydroxyl function and the peroxyester function is increasedby a carbon atom were prepared as follows:

Preparation of 7-Hydroxy-1,1,5-trimethylheptyl Peroxypivalate (C-1)

A jacketed reactor equipped with a mechanical stirrer, a thermometer anda dropping funnel was charged with 9.3 g (0.075 mole) of 45% KOH, 4.7 gof water and 11.3 g (0.058 mole) of 97.3%7-hydroxy-1,1,5-trimethylheptyl hydroperoxide. To this vigorouslystirred solution at 30° C. was slowly added 6.4 g (0.050 mole) of 94.3%pivaloyl chloride over a period of 20 minutes. The resulting mixture wasthen vigorously stirred for one hour at 30° C. after which it was cooledto 15° C. and 100 ml of pentane and 25 ml of water were added. Afterseparating and discarding the aqueous phase the product solution waswashed at 10° to 15° C. with 20 g of buffered sodium sulfite solution(consisting of 0.8 g of acetic acid, 1.2 g of sodium acetate, 2.0 g ofsodium sulfite and 16 g of water), with 15 ml of water and then with 20g of 7.7% sodium hydrogen carbonate solution. The resulting pentanesolution was then dried over anhydrous MgSO₄ and after separation of thespent desiccant by filtration the pentane was removed in vacuo at 0° to10° C. leaving 8.2 g of liquid product. The assay of the productaccording to peroxyester active oxygen was 69.6% and the corrected yieldwas 41.7%. An infrared spectrum of the product showed a strong, broad OHband centered at 3400 to 3500 cm⁻¹.

Preparation of 7-Hydroxy-1,1,5-trimethylheptyl Peroxyneodecanoate (C-2)

The same procedure as used in the preparation of C-1, supra, wasemployed for the preparation of 7-hydroxy-1,1,5-trimethylheptylperoxyneodecanoate using as the starting materials7-hydroxy-1,1,5-trimethylheptyl hydroperoxide and neodecanoyl chloride.The liquid product was obtained in 84.3% assay and 72.5% correctedyield. An infrared spectrum of the product showed a strong, broad OHband centered at 3400 to 3500 cm⁻¹.

Preparation of 7-Hydroxy-1,1,5-trimethylheptyl Peroxyneohexanoate (C-3)

Employing the reactants 7-hydroxy-1,1,5-trimethylheptyl hydroperoxideand neohexanoyl chloride and using the same procedure as used for thepreparation of C-1, the title peroxyester,7-hydroxy-1,1,5-trimethylheptyl peroxyneohexanoate, was prepared in anassay of 86.1% and a corrected yield of 71%. An infrared spectrum of theproduct showed a very large OH band centered at about 3450 cm⁻¹.

Preparation of 7-Hydroxy-1,1,5-trimethylheptyl Peroxy(2-Ethylhexanoate)(C-4)

The title peroxyester, 7-hydroxy-1,1,5-trimethylheptylperoxy-(2-ethylhexanoate), was prepared in an assay of 88.7% and acorrected yield of 78.0% by using the procedure employed in thepreparation of C-1 using as reactants 7-hydroxy-1,1,5-trimethylheptylhydroperoxide and 2-ethylhexanoyl chloride. An infrared spectrum of theproduct showed a moderate OH band centered at about 3450 to 3500 cm⁻¹.

Preparation of 4-Hydroxy-1,1,4,4-Tetramethylbutyl Peroxypivalate (C-5)

A jacketed reactor equipped with a mecahnical stirrer, a thermometer anda dropping funnel was charged with 18.7 g (0.150 mole) of 45% KOH, 15.0g of water, 27.6 (0.120 mole) of 77.6% (wetted solid)2,5-dimethyl-2,5-dihydroperoxyhexane and 100 ml of methylene chloride.To the resulting two liquid phase mixture at 28° to 30° C. was added12.8 g (0.100 mole) of 94.3% pivaloyl chloride over a period of about 30minutes. The resulting mixture was then stirred for 2.0 hours at 28° to30° C. after which the mixture was cooled to 15° to 20° C. and wasallowed to separate into phases. The upper aqueous layer was removed andwas discarded. The resulting product solution was then washed with 50 mlof 20% KOH solution at 0° C. and then with 50 ml of 7.7% sodium hydrogencarbonate solution at 15° to 20° C. The methylene chloride solution wasthen cooled to 0° to 10° C. and was reacted with 187 g of bufferedsodium sulfite solution (consisting of 7.6 g of acetic acid, 8.4 g ofsodium acetate, 19 g of sodium sulfite and 152 g of water) in order tocovert the 4-hydroperoxy-1,1,4,4-tetramethylbutyl peroxypivalate thatwas formed in the peroxidation reaction to4-hydroxy-1,1,4,4-tetramethylbutyl peroxypivalate, the desired product.A thick emulsion resulted which required three days of storage in therefrigerator to separate into two liquid phases. The upper aqueous layerwas removed and an equal volume of diethyl ether was added in order tofacilitate further processing. The solution was dried over anhydrousMgSO₄ and after separation of the spent desiccant by filtration thesolvents were remove in vacuo at 0° to 10° C. Some solids were removedby filtration and the resulting liquid weighed 20.4 g. The assay of theproduct was 90.3% according to peroxyester active oxygen content. Thecorrected yield was 74.9%. An infrared spectrum of the product showed abroad OH band centered at 3300 to 3400 cm⁻¹.

Preparation of 4-Hydroxy-1,1,4,4-Tetramethylbutyl Peroxyneodecanoate(C-6)

Reacting neodecanoyl chloride with 2,5-dimethyl-2,5-dihydroperoxyhexanefollowed by reducing the intermediate product with a buffered sodiumsulfite solution employing the same procedure as used in preparation ofC-5 resulted in the preparation of 4-hydroxy-1,1,4,4-tetramethylbutylperoxyneodecanoate. The liquid product had an assay of 91.7% and wasobtained in a corrected yield of 55.1%. An infrared spectrum of theproduct showed a broad OH band centered at 3300 to 3500 cm⁻¹.

EXAMPLE 3 Preparation of 3-Hydroxy-1,1-Dimethylpropyl Peroxyneodecanoate(I-8)

The procedure employed for preparation of 3-hydroxy-1,1-dimethylbutylperoxyneodecanoate in Example 2 (without the PTC) was used in thisexample for preparing 3-hydroxy-1,1-dimethylpropyl peroxyneodecanoatefrom neodecanoyl chloride and 3-hydroxy-1,1-dimethylpropylhydroperoxide. The assay of the product was 66.0% according toperoxyester active oxygen content and the correct yield was 65.1%. Theinfrared spectrum showed a broad OH band centered at 3350 to 3450 cm⁻¹.

EXAMPLE 4 Preparation of 3-Hydroxy-1,1-Dimethylpropyl Peroxyneohexanoate(I-9)

The procedure employed for preparation of 3-hydroxy-1,1-dimethylbutylperoxyneohexanoate in Example 2 (without the PTC) was used in thisexample for preparating 3-hydroxy-1,1-dimethylpropyl peroxyneohexanoatefrom neohexanoyl chloride and 3-hydroxy-1,1-dimethylpropylhydroperoxide. The assay of the product was 54.3% according toperoxyester active oxygen content and the corrected yield was 42.7%. Aninfrared spectrum of the product showed a broad OH band centered at 3400to 3450 cm⁻¹.

EXAMPLE 5 Vinyl Chloride Suspension Polymerizations EmployingHydroxy-t-Alkyl Peroxyesters as Free-Radical Initiators

Several hydroxy-t-alkyl peroxyesters of the instant invention werecomparatively evaluated with art t-butyl peroxyesters derived from thesame carboxylic acids in vinyl chloride suspension polymerizations at50° C. and 55° C. The vinyl chloride suspension polymerization procedurethat was employed is described below.

Suspension Polymerizations

Polymerizations of vinyl chloride in suspension were carried out in a1.5 liter reactor, which was designed and instrumented such that thepolymerization could be monitored calorimetrically. The reactor wasimmersed in a water bath, maintained 0.5° C. above the desired reactiontemperature, thus preventing any heat loss to the surroundings. The heatproduced from the exothermic polymerization plus the heat passed intothe reactor from the water bath were removed by the passage of coolingwater through internal coils in the reactor. Thus, the temperature waskept constant. The flow rate of the cooling water and the temperaturedifference between entrance and exit streams were monitored, thusproducing a continuous recording of heat removed (cal. min⁻¹).

The pressure in the reactor was also continuously monitored. At about70% conversion of monomer to polymer, the monomer in the vapor phasebecame depleted and the pressure fell. Thus, from a knowledge of thepoint of 70% conversion and the heat of polymerization of vinyl chloride(23 Kcal/mole), it was possible to calculate the "background count" inthe calorimetric recording; this background was due to heat flow fromthe water bath to the reactor. By substraction, the true rate ofpolymerization (cal. min⁻¹), as function of time, was obtained.

In the polymerization the following sequence of operations was followed:

(1) The reactor was assembled and tested for leaks.

(2) The water bath around the reactor was heated to 0.5° C. above thedesired reaction temperature.

(3) The cooling water bath was heated to 10° C. less than the reactiontemperature.

(4) The aqueous phase plus suspending agents (described later) washeated to 10° C. above the desired reaction temperature, and chargedinto the reactor.

(5) The initiator compositions were added and the filling port sealed.

(6) The reactor was evacuated by the use of a water aspirator.

(7) The vinyl chloride (200 g) was added, by displacement with nitrogen,from a small cylinder, the reactor was pressurized with nitrogen toabout 150 psi (guage). The addition of the cold vinyl chloride reducedthe temperature of the aqueous phase to a point close to the desirereaction temperature.

(8) Stirring was commenced.

(9) The reactor controllers were switched on beginning automatic controlof the temperature and continuous recording of heat output and pressure.

(10) After the pressure drop was observed, the pressure, temperature andheat of polymerization were further monitored for another one to twohours. The reactor data after the pressure drop were then used todetermine the rate of pressure drop, ΔP/Δt. The ΔP/Δt was an importantvalue since it was a measure of the rate of polymerization after onsetof the pressure drop. The larger the absolute value of ΔP/Δt the higherthe rate of polymerization after the pressure drop and the higher thepercent conversion of vinyl chloride monomer to polyvinyl chloride.After these data were obtained, the remaining vinyl chloride andnitrogen were vented and the reactor dismantled for cleaning.

    ______________________________________                                        Suspension System Used (pH˜ 6.5)                                        ______________________________________                                        1% solution of Aerosol MA 80%*                                                                        42 ml                                                 1% solution of Methocel F 50**                                                                       168 ml                                                 Triply distilled water 469 ml                                                 ______________________________________                                         *Surfactant made by American Cyanamid Co. (sodium dihexyl sulfosuccinate)     **Hydroxypropyl methyl cellulose polymer made by Dow Chemical.                Note: pH of the aqueous phase was measured at ambient temperatures,           22° C., using a standard pH meter.                                

                                      TABLE II                                    __________________________________________________________________________    Vinyl Chloride Suspension Polymerization                                      Efficiencies of Hydroxy-t-Alkyl Peroxyesters                                                                Time to                                                                            Rate of                                                                  Press.                                                                             Press. Drop                                Peroxyester                                                                         Peroxyester Level                                                                           Polymer Conditions                                                                      Drop,                                                                              ΔP/Δt,                         Employed                                                                            P/HPM.sup.1                                                                        MOLES/HGM.sup.2                                                                        Temp., °C.                                                                    pH MINS psi/M                                      __________________________________________________________________________    I-1   0.075                                                                              3.44 × 10.sup.-4                                                                 55     ˜6.5                                                                       230  -12                                        A-1   0.060                                                                              3.44 × 10.sup.-4                                                                 55     ˜6.5                                                                       440  -18                                        I-2   0.119                                                                              5.12 × 10.sup.-4                                                                 55     ˜6.5                                                                       170  -44                                        A-2   0.096                                                                              5.10 × 10.sup.-4                                                                 55     ˜6.5                                                                       250  -20                                        A-3   0.104                                                                              5.14 × 10.sup.-4                                                                 55     ˜6.5                                                                       240  -24                                        I-3   0.125                                                                              4.33 × 10.sup.-4                                                                 55     ˜6.5                                                                       180  NA*                                        I-3   0.099                                                                              3.42 × 10.sup.-4                                                                 50     ˜6.5                                                                       310  NA*                                        A-4   0.125                                                                              5.11 × 10.sup.-4                                                                 55     ˜6.5                                                                       270  -15 to -17                                 A-5   0.132                                                                              5.11 × 10.sup.-4                                                                 55     ˜6.5                                                                       240  -17                                        C-3   0.148                                                                              5.13 ×  10.sup.-4                                                                55     ˜6.5                                                                       300  -26                                        C-5   0.091                                                                              3.48 × 10.sup.-4                                                                 55     ˜6.5                                                                       >450.sup.3                                                                         NA*                                        __________________________________________________________________________     *NA -- not available.                                                         .sup.1 P/HPM -- Parts per hundred parts monomer.                              .sup.2 MOLES/HGM -- Moles per hundred grams monomer.                          .sup.3 No pressure drop observed up to 450 minutes.                      

Table II summarizes the times that were required for reaching the onsetof pressure drop [ca. 70% conversion of vinyl chloride monomer topolyvinyl chloride (PVC)] and the rate of pressure drop (ΔP/Δt) afteronset of the pressure drop when the hydroxy-t-alkyl peroxyesters of thisinvention, i.e., 3-hydroxy-1,1-dimethylbutyl peroxypivalate (I-1),3-hydroxy-1,1-dimethylbutyl peroxyneohexanoate (I-2) and3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate (I-3), were evaluated andcompared to the corresponding t-alkyl peroxyesters of the prior art,i.e., t-butyl peroxypivalate (A-1), t-butyl peroxyneohexanoate (A-2),t-amyl peroxyneohexanoate (A-3), t-butyl peroxyneodecanoate (A-4) andt-amyl peroxyneodecanoate (A-5). The time to pressure drop resultsunexpectedly and surprisingly showed that the hydroxy-t-alkylperoxyesters of this invention (e.g. I-1, I-2 and I-3) weresignificantly more efficient on an equal molar basis than were thecorresponding t-alkyl peroxyesters of the prior art (e.g., A-1, A-2,A-3, A-4, and A-5, respectively). These results significantly advancethe peroxide and the vinyl chloride polymerization art, sincehydroxy-t-alkyl peroxyesters of the instant invention are required insignificantly lesser amounts than are the corresponding prior artt-alkyl peroxyesters. This means that a PVC producer would not only usesignificantly less of the hydroxy-t-alkyl peroxyesters of this inventionfor producing the same amount of PVC (see results in Table II for I-3vs. A-4 and A-5) but he would also have to store less of the inventionhydroxy-t-alkyl peroxyesters in his refrigerated storage facilities.Therefore, the initiator costs to the PVC producer would be considerablyreduced if the PVC producer were to employ the more activehydroxy-t-alkyl peroxyesters of this invention for polymerizing vinylchloride.

Table II also summarizes vinyl chloride suspension efficiency data fortwo other hydroxy-t-alkyl peroxyesters, 7-hydroxy-1,1,5-trimethylheptylperoxyneohexanoate (C-3) and 4-hydroxy-1,1,4,4-tetramethylbutylperoxypivalate (C-5). Comparing the efficiency of inventionhydroxy-t-alkyl peroxyester I-2 with that of C-3 and the efficiency ofinvention hydroxy-t-alkyl peroxyester I-1 with that of C-5, theefficiencies of invention hydroxy-t-alkyl peroxyester I-1 and I-2 weresignificantly better than were those of C-5 and C-3, respectively.Hence, these results demonstrated the criticalness that the inventionhydroxy-t-alkyl peroxyesters must have one carbon atom between theR--C(O)--OO--C(CH₃)₂ -- group and the HOCR₃ R₄ -- group. If two carbons(e.g., C-5) or five carbons (e.g., C-3) are present, the resultinghydroxy-t-alkyl peroxyesters are significantly less efficient than theinvention hydroxy-t-alkyl peroxyesters (e.g., I-1 and I-2).

EXAMPLE 6 SPI Exotherms of the Hydroxy-t-Alkyl Peroxyesters of thisInvention

The unsaturated polyester resin in this example was a mixture of anunsaturated polyester and styrene monomer. The unsaturated polyester wasan alkyd resin made by esterifying the following components:

    ______________________________________                                        Component              Quantity                                               ______________________________________                                        Maleic anhydride       1.0 mole                                               Phthalic anhydride     1.0 mole                                               Propylene glycol       2.2 moles                                              ______________________________________                                    

To the resulting resin was added 0.013% by weight of hydroquinoneinhibitor. The alkyd resin had an Acid No. of 45-50. Seven (7) parts byweight of the above polyester (alkyd resin) were diluted with three (3)parts by weight of monomeric styrene. The resulting unsaturatedpolyester resin had the following properties:

    ______________________________________                                        a. Viscosity (Brookfield No. 2 at 20 r.p.m.)                                                            13.0 poise                                          b. Specific gravity        1.14                                               ______________________________________                                    

Curing Procedure

Gelation and cure characteristics of various initiators in the aboveunsaturated polyester resin were determined using the Standard SPIExotherm Procedure ("SPI Procedure for Running Exotherm Curves-PolyesterResins", published in the Preprint of the 16th AnnualConference--Reinforced Plastics Division, Society of the PlasticsIndustry, Inc. February 1961). Using the procedure at 82° C. severalhydroxy-t-alkyl peroxyesters of this invention were evaluated andcompared to the results employing prior art t-alkyl peroxyesters derivedfrom the same carboxylic acids. The results are summarized in Table IIIand show that the hydroxy-t-alkyl peroxyester of this invention, I-1,I-2 and I-3, are more active than the corresponding t-butyl peroxyestersA-1, A-2 and A-4, respectively, of the art as judged by significantlyshorter cure times.

                  TABLE III                                                       ______________________________________                                        82° C. SPI Exotherm Data for                                           Hydroxy-t-Alkyl Peroxyesters                                                  (1.0% by weight of pure peroxide used)                                                                     Peak                                                            Gel,   Cure,  Exotherm,                                                                             Barcol                                   Curing Catalyst                                                                              Mins   Mins   °F.                                                                            Hardness                                 ______________________________________                                        3-Hydroxy-1,1-dimethyl-                                                                      0.10   1.05   373     45-50                                    butyl Peroxypivalate                                                          (I-1)                                                                          .sub.-t-Butyl Peroxypivalate                                                                0.50   1.30   398     45-50                                    (A-1)                                                                         3-Hydroxy-1,1-dimethyl-                                                                      0.20   1.00   396     45-50                                    butyl Peroxyneohexa-                                                          noate (I-2)                                                                    .sub.-t-Butyl Peroxyneohexan-                                                               0.20   1.40   369     45-50                                    oate (A-2)                                                                    3-Hydroxy-1,1-dimethyl-                                                                      0.15   1.00   376     45-50                                    butyl Peroxyneode-                                                            canoate (I-3)                                                                  .sub.-t-Butyl Peroxyneode-                                                                  0.20   1.30   370     45-50                                    canoate (A-4)                                                                 ______________________________________                                    

EXAMPLE 7 82° C. SPI Exotherms of the Hydroxy-t-Alkyl Peroxyesters ofthis Invention Compared to Art Peroxyesters

The unsaturated polyester resin and the procedure used in this examplewere those employed in Example 6. The prior art compounds,3-benzoyloxy-1,1-dimethylbutyl peroxybenzoate (A-6) of U.S. Pat. No.3,236,872 and4-(3-hydroxy-1,1-dimethylbutyl-peroxycarbonyl)-3-hexyl-6-[7-(3-hydroxy-1,1-dimethylbutylperoxycarbonyl)heptyl]cyclohexene (A-7) of U.S. Pat. No. 4,079,074, were prepared according tothe procedures outlined in the Prior art references. Although the3-hydroxy-1,1-dimethyl-butyl peroxyesters of this invention can beprepared without appreciable contamination by the correspondingesterperoxyester (Structure C, infra) by reacting3-hydroxy-1,1-dimethylbutyl hydroperoxide with the corresponding acidchloride, the 3-hydroxy-1,1-dimethylbutyl peroxyesters could not beprepared from 3-hydroxy-1,1-dimethylbutyl hydroperoxide and aromaticacid chlorides. In particular, attempts to prepare3-hydroxy-1,1-dimethylbutyl peroxybenzoate (A-8) from3-hydroxy-1,1-dimethylbutyl hydroperoxide and benzoyl chloride producedvery little of the desired product, A-8. Instead, the product was mostlyA-6 which meant that benzoyl chloride reacts too readily with the HO--group of 3 -hydroxy-1,1-dimethylbutyl hydroperoxide and the HO-- groupof A-8. On the other hand the acid chlorides that are used in theprocesses for producing the instant invention peroxyesters surprisinglyreact significantly less readily with the HO-group of3-hydroxy-1,1-dimethylbutyl hydroperoxide and the HO-group of the3-hydroxy-1,1-dimethylbutyl peroxyesters of this invention. Thus, thehydroxy-t-alkyl peroxyesters A of this invention are the dominantreaction products.

The following Table IV summarizes the 82° C. (180° F.) SPI exotherm datawhen 1.0% by pure weight of various peroxyesters were used to cure theunsaturated polyester resin. The invention peroxyesters employed were3-hydroxy-1,1-dimethylbutyl peroxy-(2-ethylhexanoate) (I-6) and3-hydroxy-1,1-dimethylbutyl peroxyneohexanoate (I-2) whereas the priorart compounds evaluated were A-6, A-7, t-butyl peroxy-(2-ethylhexanoate)(A-9) and t-butyl peroxybenzoate (A-10).

                  TABLE IV                                                        ______________________________________                                        82° C. (180° F.) SPI Exotherm Data                              (1% By weight of Pure Peroxyester)                                                     Gel,                         Barcol                                  Peroxyester                                                                            Mins   Cure, Mins                                                                              Peak Exotherm, °F.                                                                 Hardness                                ______________________________________                                        I-2      0.2    1.0       386         45-50                                   I-6      1.6    2.4       382         40-50                                   A-9      5.5    6.7       388         45-50                                   A-7      11.5   14.5      375         33-45                                   A-6      40.4   53.4      294          0-40                                    A-10    No Gel up to 50 minutes                                              ______________________________________                                    

The results in Table IV show that the invention3-hydroxy-1,1-dimethylbutyl peroxyesters of this invention (i.e., I-2and I-6) were significantly more active in the unsaturated polyesterresin than were the art peroxyesters as judged by shorter gel and curetimes and/or by enhanced hardness [compare the results for inventionperoxyester I-6 with those for prior art peroxyesters A-9, A-7, A-6 andA-10].

What is claimed is:
 1. A process of polymerizing ethylenicallyunsaturated monomers comprising adding to the reaction mass of saidmonomers an initiating amount of a hydroxy-t-alkyl peroxyester of thestructure ##STR7## having a ten-hour half-life temperature below about75° C., where R₁ and R₂ are selected from alkyl of 1 to 4 carbons,R₃ andR₄ selected from hydrogen or alkyl of 1 to 4 carbons, R₁ and R₃ can beconnected together to form a lower alkyl substituted 3 carbon atomalkylene bridge and R₃ can additionally be ##STR8## and R is selectedfrom ##STR9## where R₅ is selected from hydrogen or alkyl of 1 to 8carbons, R₆ is selected from alkyl of 1 to 8 carbons, R₇ is selectedfrom the group consisting of alkyl of 1 to 8 carbons, alkenyl of 1 to 8carbons, alkoxy of 1 to 6 carbons, and aryloxy of 6 to 10 carbons, andR₈ and R₉ are selected from alkyl of 1 to 4 carbons, and polymerizingsaid reaction mass until completion.
 2. A process of curing anunsaturated polyester resin composition comprising adding to thereaction mass of said unsaturated polyester resin composition acatalyzing amount of a hydroxy-t-alkyl peroxyester of the structure##STR10## having a ten-hour half-life temperature below about 75° C.,where R₁ and R₂ are selected from alkyl of 1 to 4 carbons,R₃ and R₄ areselected from hydrogen or alkyl of 1 to 4 carbons, R₁ and R₃ can beconnected together to form a lower alkyl substituted 3 carbon atomalkylene bridge and R₃ can additionally be ##STR11## and R is selectedfrom ##STR12## where R₅ is selected from hydrogen or alkyl of 1 to 8carbons, R₆ is selected from alkyl of 1 to 8 carbons, R₇ is selectedfrom the group consisting of alkyl of 1 to 8 carbons, alkenyl of 1 to 8carbons, alkoxy of 1 to 6 carbons, and aryloxy of 6 to 10 carbons, andR₈ and R₉ are selected from alkyl of 1 to 4 carbons, as the curing agentand heating the reaction mass until completion.
 3. The process of claim1 wherein the ethylenically unsaturated monomer is vinyl chloride orethylene.
 4. The process of claim 3 wherein the initiator forpolymerizing vinyl chloride monomer is selected from the groupconsisting of 3-hydroxy-1,1-dimethylbutyl peroxypivalate,3-hydroxy-1,1-dimethylbutyl peroxyneohexanoate, and3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate.
 5. The process of claim2 wherein the curing catalyst is selected from the group consisting of3-hydroxy-1,1-dimethylbutyl peroxypivalate, 3-hydroxy-1,1-dimethylbutylperoxyneohexanoate, 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate, and3-hydroxy-1,1-dimethylbutyl peroxy-2-ethylhexanoate.